Re: Need help with vocal booth/ room dimensions
Posted: Thu Feb 28, 2019 8:42 am
The HS8 is an active speaker: built-in amplifiers. So there's no problems with having long cables to get to the speakers. There won't be any losses in quality due to the extra length. Assuming you are using balanced cables, of course! You could make them 300 feet long, and still not have any issues.I will have to buy much longer speaker wires in order to do this, was trying to avoid having to do that, but after seeing the graph and response I think I'll run to the store and try it out!
Keeping them away from the front wall is fine, .... IF you have a room that is large enough! But 4-5 feet is not enough. Here's a chart that shows the problematic distances in red, the not-so-good distances in blue, and the best distances in green:1) I believe the user manual for the Yamaha HS8 are reccomends the monitors be placed 4-5 ft away from the front wall. I believe they are rear ported and have a switch to compensate some if the monitors are being placed closer to the front wall. Should I ignore the manufacturer recommendation and move them close to the front wall anyways? If I do this, should I use the switch in the back to account for this?
The chart is published by Neumann, but it applies to all speakers, made by all manufacturers. It's a physical problem that affects everything the same, not specific to any manufacturer.
As you can see, the worst distance is about 4 to 5 feet! That's in the middle of the red range, as it produces SBIR dips in the range of 65 Hz to 45 Hz...
To get to a sort-of OK position, it needs to be at least 7 feet form the front wall, which is not possible in a small room, and it only gets to be "good" beyond about 10 feet.On the other hand, if you put it right up against the front wall (less than 16 inches), then that's "good" too.
So I'm not sure why the manual for your speaker says 4-5 feet: that doesn't make much sense, and you can see the exact problem in your own results.
Set then up against the front wall, with just a 4" gap where you can insert a 4" panel of good absorption, such as OC-703 between the speaker and the wall.
Rear-porting is not a problem. You can place your speaker close to the wall if you need to. In fact, the manual says this as well: "In situations where it is not possible to position the speakers a sufficient distance from walls or corners, the ROOM CONTROL switch can be used compensate for excessive bass. As you move the speaker closer to walls or corners, a higher compensation setting may be required to achieve natural sounding response ...". So there's no problem with that: it won't damage your speaker if you put it close to the front wall, with the rear corner of the speaker just 4" away from the wall.they are rear ported and have a switch to compensate some if the monitors are being placed closer to the front wall.
No problem at all. The propagation of electric signals in copper wire is very nearly as fast as the speed of light, around 300 million meters per second, so unless one cable is a few million meters longer than the other, there won't be any difference at all in arrival of the signals. You would get a much, MUCH larger difference just by moving one speaker one millimeter closer than the other. So, no: there won't be any difference at all. The two channels will sound exactly the same, no loss of quality, no delays, no phase shift, no imaging issues, nothing.2) Does it matter if one cable is say 50ft long and the other monitor cable is only 10ft long? Will this cause any delays, damage the stereo image, loss of quality or any other negative effects?
however, I have the monitor height at 47" from center of tweeter to the floor. I couldnt find any information on where the acoustical axis is, and the manual suggested having the tweeter lined up with your ear. Is this ok or is there a known acoustical axis point for yamaha hs8 that I should use instad, or should I use the midpoint between the woofer and tweeter as the acoustical axis? The acoustic axis is going to be on the imaginary line that joins the center of the woofer to the center of the tweeter, and much closer to the tweeter, which is a bit below where you estimated. So you could probably raise your speaker a bit. In fact, for most speakers and rooms, you can go a bit higher than 47", and that can be beneficial... as long as you don't go too high! Maybe an inch, or maximum 2 inches. The reason why that is good is because it reduces reflections from the surface of your desk or console. The reason why you can't go too high, is because you would put your head too far off-axis from the speaker.
Nope! Unfortunately not. The frequency is so low that any treatment would have to be huge. If you follow the theory that a porous absorber is effective at frequencies where the thickness of the absorber is 7% of the wavelength, and your frequency is 46 Hz, then your wavelength is over 24 feet! 295 inches, in fact. 7% of that is 21 inches. so you would need an absorber 21" thick on the front wallif I know where the dip is in the low frequency, could i use some room acoustic software to correct that?
Even then, it would not be very effective, since porous absorbers just don't do very well at such low frequencies...Nope! That doesn't work either, because this is a phase cancellation problem: the wave going towards the wall bounces back, and cancels itself out. So if you try to EQ that, and boost the frequency that is missing, all you do is get a BIGGER cancellation! You make the dip even deeper. But since you can't actually destroy energy, all the extra power that you are pumping in with your EQ boost has to go somewhere, and normally it just ends up causing instability around that frequency, so you end up with a very long ringing tone at an adjacent frequency (something like "feedback").Is there a way to have the software add it back in?
That's what I meant when I said it was "impossible or extremely hard" to treat such a problem. The frequency is just too low, and it is a phase cancellation problem, so it cannot be equalized.
Sorry!
That's a good start, but there are 12 corners in a room, not just 4....I plan filling all 4 corners with roxul safe n sound asap.
You set the INDIVIDUAL speakers to 80 dBC for each one, but then when both are playing back the same sound together, the total will be 86 dB. Because twice the power is the same as an increase of 6 dB, and with both speakers on, the total is twice the power. That assumes that your speakers are playing in phase, of course, and that it is the exact same sound going out through both (in other words "coherent sound"). If the sound is not coherent, then the increase in level will be less: probably around 3 dB. So this is a good test to make sure your speakers and sound system is performing fine: test each speaker by itself at 80 dB with the other one turned off, then put them both on and you should see 86 dB. If you don't get 86 dB, then there's something wrong...I had my meter set to "C", "Slow", but I had a level of 80db. Is "86" a typo, or should I run the next test at 86 db?
Finding the best location for your speakers and mix position can take a long time! I'm just giving you the basics here: the starting point. Set them up against the front wall with 4" of absorption behind them, set up your chair at about 1/3 of the distance from the front wall to the back (anywhere in the range 30% to 40% is a good starting point), aim the speakers at a spot about 16" behind your head, then do multiple REW tests with the mic and speakers in slightly different positions to see if there's a better location. Move one thing at a time, in small increments, then keep the best location for that "thing". Then move another thing in small increments, to optimize that one. Then something else. Then go back to the first thing. For example, first try moving the mic forward and backward in steps of a couple of inches, to see if there's a good improvement overall. Then try moving the speakers further apart or closer together (also in small steps of a couple of inches). Then try moving the speakers up or down a little (in very small steps: half an inch or so). Then when you have all three of those done, go back to the mic position, because there might be an even better place now... etc.Im anxious to get up and running and am hoping I can at least get the baseline and monitor position established asap
Optimizing this can take a long time... and then when you have your treatment in, you can do it all over again, since the best location will probably now be somewhere else!
As the saying goes, Rome wasn't built in a day.... and your speaker / mix position layout can't be done in a day either!
- Stuart -
It's a slow process.
